Abstract [en]

The unbound nucleus 12Li is evaluated by studying three-neutron one-proton excitations within the multistepshell model in the complex energy plane. It is found that the ground state of this system consists of anantibound 2− state. A number of narrow states at low energy are found which ensue from the coupling ofresonances in 11Li to continuum states close to threshold.

Xu, Zhenxiang

Abstract [en]

The properties of unbound nuclei 12Li and 13Li are calculated within themultistep shell model in the complex energy plane by assuming that the spectraare determined by the motion of neutrons outside the 9Li core. It is foundthat in 12Li the ground state consists of an antibound 1/2+ state and thatonly this and a 1/2− and a 5/2+ excited states are physically meaningfulresonances. Calculations suggest that there is no bound or antibound statein 13Li.

Xu, Zhenxiang

KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.

2012 (English)Doctoral thesis, comprehensive summary (Other academic)

Abstract [en]

In this thesis the properties of unbound nuclei like 12,13Li are studiedby extending the multistep shell model to the complex energy plane. Thenuclei 12Li and 13Li are described starting from the one-particle states in 10Liand two-particle states in 11Li. The ground state of 12Li is found to be anantibound state. No bound or antibound state is found in 13Li. It is alsoshown that the odd proton plays a minor role in these nuclei.This framework is also applied to study the recently proposed spin-alignedproton-neutron pair coupling scheme. For this the MSM is extended to theproton-neutron space as well as the isospin space. In the model, a nonorthogonalbasis is introduced, which allows us to identify simultaneously theroles played by all configurations. The four-particle, six-particle and eightparticlenuclei in the heaviest N = Z region are evaluated using the MSMbasis within the space spanned by the single 0g9/2 hole shell.A novel Monte Carlo representation in the complex energy plane is alsodeveloped for studying nuclear excitations in the continuum. The calculationson realistic potentials show a stable performance and high accuracy in the oneparticleand two-particle cases. This will provide a convenient tool to studyopen systems with many nucleons in the continuum.